1. Field of the Invention
The present invention relates to a transmission line assembly in which a transmission line is formed on a dielectric plate, an integrated circuit incorporating the transmission line assembly, and a transmitter-receiver apparatus incorporating the integrated circuit, such as a radar apparatus or a communications apparatus.
2. Description of the Related Art
Hitherto, integration of a waveguide transmission line with a dielectric substrate has been proposed in (1) Japanese Unexamined Patent Application Publication No. 6-53711 and (2) Japanese Unexamined Patent Application Publication No. 10-75108.
In a waveguide transmission line assembly according to (1), in a dielectric substrate having two or more conductor layers, two lines of through holes are provided, each line having a plurality of through holes electrically interconnecting the conductor layers, so that the space between the two interconnected conductor layers and the two lines of through holes operate as a waveguide (a dielectric-filled waveguide). In a dielectric waveguide line and a wiring board according to (2), in addition to the construction described above, conductor sub-layers electrically connected to the through holes are formed between the two main conductor layers, and outside the lines of through holes.
However, in both (1) and (2), the through holes arranged in planes which extend in a direction perpendicular to the waveguide (and each hole being arranged perpendicular to the plane of the dielectric substrate), are the only current paths which operate as walls; thus, current concentrates in the through holes, resulting in the problem of increased conductor loss. Furthermore, the through holes formed in the direction perpendicular to the plane of the dielectric substrate allow current to flow only in the direction perpendicular to the dielectric substrate, and do not allow current to flow in the diagonal direction, resulting in the problem that the transmission characteristics are not as good as compared to a common waveguide or a dielectric-filled waveguide.
The present invention provides a transmission line assembly, an integrated circuit incorporating the transmission line assembly, and a transmitter-receiver apparatus incorporating the integrated circuit, such as a radar apparatus or a communications apparatus, which serves to improve productivity by forming a waveguide transmission line on a dielectric plate, in which integration with a wiring board is achieved, and which serve to improve transmission characteristics.
To this end, the present invention, in one aspect thereof, provides a transmission line assembly including a dielectric plate having a continuous protruding portion on at least one of the surfaces thereof so as to form a convex section; electrodes formed on both of the surfaces of the dielectric plate including the outer surface of the protruding portion; and a plurality of through holes arrayed on each side along the protruding portion, each electrically interconnecting the electrodes formed on both of the surfaces of the dielectric plate. Accordingly, a waveguide transmission line with a low transmission loss can be implemented using a dielectric plate, and furthermore, an apparatus in which components are mounted on a flat surface of a dielectric plate can be readily implemented.
Preferably, in the transmission line assembly, the protruding portion on a dielectric substrate is formed of a dielectric material having a dielectric constant larger than that of the dielectric plate, serving to reduce loss associated with radiation from through holes, so that a dielectric waveguide with small loss, high reliability, and small in size can be readily implemented.
Preferably, in the transmission line assembly, if the dielectric constant of the protruding portion and a region surrounded by a plurality of through holes in a dielectric plate is made larger than that of the other regions, the distribution of magnetic field in the waveguide portion becomes further concentrated, serving to implement a dielectric waveguide with small loss.
In the transmission line assembly, the distance between the electrodes at the protruding portion in the thickness direction of the dielectric plate is preferably at least as long as half the wavelength in the dielectric plate at the operating frequency. Accordingly, unwanted transmission modes can be effectively suppressed.
Further, in the transmission line assembly, the pitch of the plurality of through holes in the direction along the protruding portion is preferably not longer than half the wavelength in the dielectric plate at the operating frequency. Accordingly, unwanted transmission modes can be further suppressed.
Furthermore, in the transmission line assembly, the distance between the two pluralities of through holes in the direction across the protruding portion is not longer than the wavelength in the dielectric plate at the operating frequency. Accordingly, mode transformation to the parallel-plate mode is inhibited at the operating frequency, and loss associated therewith is eliminated, so that a transmission line with an even lower loss is achieved.
More preferably, the distance between the electrodes at the protruding portion in the thickness direction of the dielectric plate is not longer than the wavelength in the dielectric plate at the operating frequency, and the width of the protruding portion and the distance between the pluralities of through holes in the direction across the protruding portion are not longer than half the wavelength in the dielectric plate at the operating frequency. Accordingly, transmission in a single mode is achieved in the operating frequency range, preventing loss associated with transformation of mode at the bend portion and improving flexibility of layout pattern of a transmission line.
Furthermore, the corners of the protruding portion are preferably rounded. Accordingly, concentration of current at the edges of the electrodes can be alleviated, further reducing conductor loss.
Furthermore, the protruding portion is preferably tapered so as to get narrower away from the dielectric plate. Accordingly, productivity of transmission lines can be improved and cost can be reduced.
The present invention, in another aspect thereof, provides an integrated circuit including a transmission line assembly defined above; and a plurality of transmission lines formed or electronic components mounted on the dielectric plate in the transmission line assembly. Accordingly, loss can be reduced, and in particular, by making one of the surfaces of the dielectric plate flat, formation of transmission lines using conductor patterns and mounting of electronic components can be facilitated.
In the integrated circuit, the base material of the dielectric plate is preferably a ceramic material. Accordingly, mounting of surface-mount components by simultaneous reflow soldering is allowed, improving productivity and thus reducing cost.
The present invention, in yet another aspect thereof, provides a transmitter receiver apparatus including an integrated circuit defined above, a transmission line thereof being used to transmit a transmission signal and a reception signal; an oscillator; and a mixer. Accordingly, power consumption can be reduced and sensitivity can be improved.
Other features and advantages of the present invention will become apparent from the following description of embodiments of invention which refers to the accompanying drawings.